Every new camera has its limitations and the 70D is no exception. Take a look at some of the limitations of the Canon 70D with Audio recording, Aperture/shutter priority, and other settings. Some of these limitations might surprise you though none are quite as bad as not being able to change the aperture on the Nikon D7100.

I did some recordings of both the STM lens compared to the Tamron 24-70 f2.8 as well so you can hear the differences in noise for focus and aperture. You can definitely hear the Tamron while the STM is whisper quiet. But the Tamron is not loud enough that I think you would hear it from an external mic though the internal picks it up.